Hi Bryan,
Let's see if we can help you out here
1. Can you be a little more specific on the things your supervisors disagree on?
2. Your understanding about the requirement is correct, you do not need to hold a PM title nor you have to be the sole individual responsible for every processes for every projects. Have you communicated with your 2 supervisors to make sure they are aware of this fact?
3. You mentioned that you have 6+ years of experience on PM, are there other people you can approach to get the verification done?